1. Field of the Invention
This invention pertains to concrete slab and steel construction and is directed particularly a simplification in composite open web steel joist and wire mesh reinforced concrete slab construction to provide a more economical composite floor or roof structure in building construction as compared to prior art construction. In this invention the columns have floor supporting members in both major directions that are composite with the poured in place concrete slab.
2. Description of the Prior Art
The improvement in this application pertains specifically to an improvement and simplification in the composite concrete slab and steel joist construction disclosed in the inventor's copending U.S. patent application, Ser. No. 865,632, filed Dec. 29, 1977, and also disclosed in his prior U.S. Pat. Nos. 4,056,908; 3,728,835; 3,683,580; and 3,624,980. It also relates to other patents covering elements of a composite beam and joist floor system including U.S. Pat. Nos. 3,392,499; 3,457,818; 3,527,007 and copending application Ser. No. 491,696 now U.S. Pat. No. 3,967,642.
Specifically, the inventor has designed a composite system for floor framing members for use in multi-story buildings which produces a structurally superior and more economical floor system then previously available. In this system open web steel joists and the supporting beams of the steel frame are bonded to a two and one-half inch thick poured in place concrete slab to make all the structural floor members work together and act compositely with the concrete floor deck.
The unique design desclosed in the prior patents cited above accomplishes composite construction in the following way. Open web joists are fabricated with the apices of the webs projecting above the top chord of the joists. After the joists are welded to the beams, precut sheet metal pans are placed along the beam between the joist ends. These pans allow the subsequently poured in place concrete slab to rest on top of the supporting beam and completely encase the joist ends. The encased joist ends act as shear connectors between the beam and the concrete slab. Long sheets of prepunched corrugated centering are placed over the joist webs and locked in place with metal wedges. After the poured concrete hardens, all joists and beams become composite with the concrete slab.
Copending application Ser. No. 865,632 discloses the use of an open web steel truss in a composite system to replace a beam. It is not directly related to the present application, but the truss could be used with the improvement described herein.
U.S. Pat. Nos. 4,056,908 and 3,728,835 best describe and illustrate the composite construction system of the inventor. In the system of these patents, it has been assumed that all joists extending between the beams had to be of the composite construction described in U.S. Pat. No. 3,728,835. This construction, while having all the advantages described in that patent, requires that the corrugated sheet metal be prepunched along a center line of the sheet to match the selected joist spacing. This prepunching of the corrugated sheet metal has posed several problems in field use and the inventor has found it desirable to minimize the punching required in corrugated sheet metal. Furthermore, it is sometimes not necessary or even desirable to make all the joists in a floor composite with the poured in place slab. With the system of the present invention only the joists at the columns are composite, the remaining joists being composite at their ends only where they join the beams. This permits the use of standard, unpunched decking at less cost. The decking can be put in place more economically and the wedges previously used are not required for the non-composite joists. Additionally, the composite joists can be made with the webs at any convenient spacing since they do not have to match holes in the deck.
With the simplified composite system of the present invention, the floor will still act as a diaphram in both major directions due to the use of composite beams and composite joists at the columns acting at right angles to one another.